Latest Entries »

We are all seeing the start of an energy crisis. Petroulum will not last us forever and we are realizing that truth. There are other energy possibilities to move and each has its own pros and cons. Someday we will have to move ourselves to a new set of energy resources. Solar is a strong possibility for being a key energy resource.

Why is solar such a strong possibility? First of all, it is all around us. Solar power can be delivered on the small scale to power a little calculator or expanded to cover acres of land and power thousands to millions of houses. It is a free stable fusion reactor for every one, large and small. it has been combining hydrogen isotopes for billions of years before the human race existed and will continue for billions more. It is scalable, and unlike many other energy resources, it can be converted directly into usable energy. What I mean is that it is possible to convert sun light directly into electrical energy without the need to boil water or heat gases. There are no pollutants while the solar cells are in operation, which is unlike most fossil fuels.

Monocrystalline silicon solar cell

Solar energy like all other forms of energy, has its problems. For one, it is limited by time of day and weather. If it is night or bad weather the amount that solar panels produce is drastically dropped. This makes it difficult at best to see a full electric grid based off of solar alone. Another degrading factor is the expensive materials needed in make many of the solar cells in existence today. The common solar cell that has a blue tint is made from highly purified silicon. Silicon is common, for example most of the sand on a beach and quartz crystals are made of silicon oxide. The problem is purifying it so that it is usable in solar panels. Another problem that is less often discussed is that many of the higher efficiency solar cells use relativity toxic elements. Some of these include Cadmium, Selenium and Arsenic. During normal operation the chemicals are bound up and are relatively safe, but if disposed of improperly, they can lead to toxic leakage.

These facts support solar energy to be a part of the solution but not the whole solution. In the end, we will need a combination of other energy sources to stem this energy crisis. There are advances that would help improve the position of solar power.

I want to discuss some of the possibilities that will help solar energy. Understand that I have a distinct bias that is due to my present research. One of these possibilities that will help solar technology is the advent of quantum dot solar cells. I will start by breaking up the term. Quantum dots are little balls of material. Imagine taking a quantum sized ice cream scooper to a material. This ball of material has properties that are different from the material from which it came due to its small size.

Quantum dots, all excited using ultraviolet light and photoluminescencing various colors of light. The emitted light changes depending on the quantum dot's size due to quantum confinement. Reds are the largest dots and blues are the smallest.

One of these properties is called quantum confinement. I tried to discuss it on the video blog earlier, but here is a different perspective on it. Think of an unruly kid. If one gives them a whole in which park to play, they will slowly wander various places and rarely travel in a straight line until they tire themselves out. Now if it is a rainy day outside and they are confined to a house, they become a little more energetic, while not having a good method to let go of that energy. They get into trouble and you ground them to their room. Now, they get super energetic and start to become loud letting out some of that pent in energy. If you attempted to confine them any further, well you get the point. As one confines the kid he/she becomes more energetic. In a quantum system the electron acts in much the same way, as one closes the barriers around the electron, it becomes more energetic. This is a side effect of the uncertainty principle. As you confine its position in space, its momentum becomes less confined. That is to say, there is the electron but I now do not know how fast it is going. In quantum dot solar cells, this allows us to tune the electrons energies by confining them. This causes the energy of light that it can absorb efficiently to increase.

Another useful property of quantum dot solar cells is called self purification. Just as it sounds quantum dots purify themselves. If you have ever shaken a container of sand you know that as you shake it, the heavier large grains will make their way to the bottom as lighter smaller grains work their way to the top. Quantum dots do much of the same thing. If there is an impurity, it is able to shift around due to the “shaking” of atoms around it. This shaking is from room temperature heat that shakes all atoms around us. As it shifts around, there is a chance that it makes it to the surface, which is a nice comfy stable spot for it. When it is on the surface, it is out of the rest of the material and does not effect its properties. This does not happen in large materials because there is too much material between the impurity and the surface, but in quantum dots the impurities only have to jump a few hundred times to make it to the surface.

So how else can was see nano materials? We have now touched them and shot electrons through them and at them…, so how else can we see the nanoscale? Well, through what I would like to term a spooky action at a distance, which sadly has already been taken. If you want to read more on the real spooky action at a distance, I have included a link to an article at the end. This spooky action is actually not so spooky when you understand the math, but when I was reading the non math science books as a kid, it seemed really spooky. It is a processes called quantum tunneling. In the classical theory of physics for a baseball to hop over a fence, it must be given enough kinetic energy to rise over the gravitation potential energy of being above the fence. In quantum mechanics, this is not always true. A quantum particle can pass through an energy barrier that is larger than its own energy. Just like if a baseball teleported through the fence… weird quantum world strikes again.

The scanning probe microscope (SPM) is a broad category that includes the scanning tunneling microscopy (STM) and the atomic force microscope (AFM), but what they are talking about applies to the STM.

The scanning tunneling microscope (STM) uses this property to view nanostructure. First, the nanostructure is covered with a thin layer of metal or other conducting layer, then the outside surface is charged with a lot of electrons. These electrons are not very high energy, but they want to get off of the surface. The STM metal tip is brought closer to the charged surface until some of the electrons are able to tunnel through through the vacuum barrier between them and the STM tip. These electrons create a current in the metal tip. Knowing the energy of the electrons and the amount of current passing into the STM tip, we can mathematically deduce the distance between the tip and the charged surface. The STM scans the surface similar to the atomic force microscope, in lines back and forth.

One last thing, I have so far been writing this blog as a class assignment, but the class is about to end. I will continue this blog after this but I will warn that the posts may not be regular. I may feel like posting a lot some months and maybe not at all others. Particularly when dealing with the graduate school, there may be times when I am too overloaded. Until next time, cya.

Many things in science are super complex, hard to understand, and even harder to put into words. Luckily, I do not believe that the base idea behind the Atomic Force Microscope (AFM) is one of those things. Have you ever played the game where there is an object in a box and you cannot see it but you have to feel it and you have to make a guess as to what the object is? Well, this is very simply how an AFM works. Just shrunk … really really small. The AFM has a little tip that is made of a crystal sharpened to a single atom at its tip. This tip is dragged across the surface that you want to image.

Generally, how a AFM works.

Here is a depiction on how it works. The laser is able to magnify the movement of the tip onto a detector that can translate it to the height of the tip. After this passes over a surface many times, one can build up a picture.

AFMs are used when one has a relatively flat surface that one wants to image. AFMs are able to image nano objects without a large amount of preparation. Many of the other methods require that the surface to be covered with a layer of metal. The main downside is that it takes time, lots of it. Each pass has to be done individually, which becomes very time consuming especially when compared with methods such as scanning electron microscopy.

There is a lot that I am not able to cover, but this may help get a general idea about the operation of an AFM. Understand that there is a lot more that I am not getting into about its operation. I may come back and post some more on the subject, but that is all for now.

Peter Tsou looking at a large piece of aerogel at Jet Propulsion Laboratory, California Institute of Technology

Where is the border between air and solid? To put it in other words how much material does it take to make a solid? Aerogel is a very interesting material that is made of over 75% air by weight and over 99.9% by volume. It holds 15 world records including being the best insulator and lowest density solid. It is made of silica which is a main part of glass and quartz crystals, but what separates aerogel is the silica structure is in spherical particles between 2-5 nanometers in size. These particles are then arranged in lose three dimensional structure that contains pockets of air. Think of a milk crate, the crate is strong enough to stand on but it is mainly open space between plastic structure. These nano particles of silica are not neatly arranged as the milk crates plastic but the same general effect occurs.

A flower resting on a thin aerogel block as a bunsen burner is heating the bottom of the aerogel.

Why is this useful? Well this material is used in many cases that need a really good insulator from heat. The empty structure means that it is hard to transfer heat across. Think about a cup of hot chocolate, if you hold you hand a centimeter or so way you can barely feel the heat from the cup but if you touch it, you definitely feel it. This is because air as a gas has a very low density and each of the molecules do not interact with one another. Most solids such as you and the mug the atoms and molecules are tightly packed and easily interact and transfer energy. But in aerogel there is mostly air and not much actual contact between spherical nano particles of silica. This leads to slow transfer of heat from one side to the other of the solid.

Now you may be thinking why is not air or vacuum the perfect insulator? This is because there is a second type of heat transfer called radiant heat. All things emit electromagnetic radiation better known as light. This emitted radiation from heat is called blackbody radiation. At room tempature most of this light is in the inferred which is below the range of human eye sight. But if you have seen a red hot object, this red color comes from the heat emitting light in the range that we can see. Another nice property of silica is that it is good at absorbing inferred spectrum. This means that even radiant heat is absorbed into the aerogel and does not pass through. This helps make aerogel one of the best insulators.

The collector arm from the Stardust spacecraft, filled with aerogel blocks.

Aerogel is being used as heat insualtion and as a high surface area material in super compaciters. Also the Stardust spacecraft brought back samples of comet dust in aerogel. NASA needed a low density material to expose to comet dust that would not destroy the comet dust.

To see nano scale objects, one needs to look no further than a soap bubble. A soap bubble made of two layers of soap molecules with water in between. If you look at a soap bubble in the right light and at the correct angle, you can see a rainbow of colors. This is because the thickness of the bubble is on the same scale as the wavelength of light. Visible light has a larger wave length than nanoscale but it is a way that we can almost “see” something close to the nanoscale. (nm = nanometers)

The sizes are disproportionate but they do get the point across.

Another interesting point to bring up is that the soap aligns in a single layer that is 1-2 nm thick. In this and cases like it one can make multiple layers. This is used to make some nanomaterials, called Langmuir–Blodgett films.

Everyday you wash your hands or wash dishes you use a form of nanotechnology. What you might ask? Well, soap…. Soap products work by trying to make greasy substances attach to water. To understand how this works we need to know a little more about what it means to be greasy. Long hydrocarbons that is chains of carbon and hydrogen found in oils, fats and waxes all feel greasy, Why? All of these substances contain lots of accessible surface electrons. This means that they have a large Van der Walls force between them and any other substance that also have lots of accessible surface electrons. Our body does the best to interpret this molecular stickiness as greasy.

Water does not interact well with oils because it is small so there is little attraction from Van der Waals and water has its own method of interacting that is stronger called hydrogen bonding. In the end under normal circumstances water would rather stay with its own kind and not clean away any oils on the skin or the grease from dirty dishes in your sink.

Soap surrounding a large hydrocarbon

Soap is like a diplomat between these two substances on one end it is water like. It has a charged “head” that interacts well with water. But it also has a fatty, oil like “tail”, this makes it so that the oils, fats and waxes see what they like as well. When soap is added to water the tail part of the soap tries to find other tails. This continues until the soap starts to form little balls, called micella, around any grease like substance. Then these balls are carried with the water and down the drain.

In the picture, there is my best depiction of a micella. Each circle is an atom the red are oxygen, the green are carbon and the blue are hydrogen. The soap are the large chains with two oxygen(red) at the “head”. There is a large chain of carbon(green) and hydrogen(blue) which represents the oil or grease that the soap is picking up and surrounding. The little sets of red and blue are water or H2O.

Technical Info: If your like me and when you see this you start to remember your organic chemistry. And then compulsivity try naming them according to the IUPAC code, I will save you the trouble. The soap molecules are a mixture of heptanoic acid and nonanoic acid. I know that these are a little small for most soaps which usually consist of lauric acid (dodecanoic acid) and stearic acid (octadecanoic acid) but for the puposes of showing the base principle the shorter chains are easier to depict. The large hydrocarbon in the center is 4-propyl-8-methyl-tetradecane (I could be wrong my organic chemistry is a little rusty) and the small hydrocarbon is propane, and I understand that the likelihood of propane getting stuck in a soap micella is small but I needed a space filler.

I know that this is supposed to be about nanotechnology but I thought since April 1st has come and nearly passed, I would start a list of this years April Fools jokes by various people and cooperations.

Google again out did themselves on April 1st. They stated that they introduced Google motion software. It was said to use your web camera to track your movements. This would enable commands to be made through hand motions.

Hulu made there main page, revert to the internet style of 1996, and had videos load up with a dial tone. My guess it will disappear in a few hours so I provided a screenshot below for those who missed out.

Hulu reverts to 1996

Feel free to comment about any April Fools jokes you make have stumbled upon on the internet!

How would one move an atom? First one must be able to see it. The three commonly used ways of seeing nano structures directly are the:

Electron Microscope

Atomic Force Microscope (AFM)

Scanning Tunneling Microscope (STM)

Image of a snowflake was processes with a platinum coating

The electron microscope sends a beam of electrons that acts like light to produce an image of the object. It is similar to any visible light microscope. One shines a light on or behind the object and then looks at the light that has either been reflected or passed through the sample. But light is just too big for most objects on the nano scale.

To get the idea of this, think of light like ripples on a pond. The ripples interact with objects and may change direction or get blocked. For large objects, for example a boat, this effect is large. One can easily see a ripple on a pond would get blocked by a row boat. But if I were to try and see a little piece of saw dust, smaller than the wavelength of the ripple, it would be near impossible to see any effect on the ripple. The saw dust is small enough to move up and down with the ripple and in the end causes almost no measurable effect to the ripple. This is like using light looking at a nano object. It just passes over without making a noticeable impact.

Due to the interesting properties of the quantum world, all matter can exhibit wave like behavior. It turns out that electrons at the nano scale act like waves but their wavelength is much smaller than that of visible light. This means that even the nano particles look like a boat relative to the ripple on the pond. To add a little more detail and perspective, visible light is defined to have a wavelength 380 to 750 nanometer, which is much larger than nano scale objects, but electrons in the electron microscope are between 1-100 picometer or .001-.1 nanometers.

There are also more complicated secondary effects that can tell us information about the material in question. Electron microscopes are best for viewing large nano objects on the order of 100-1000s of atoms in size. Most objects need to be prepared with various things such as conductive coatings and put in a vacuum environment. This preparation usually makes it hard, if not impossible, to view living objects.

There is a lot more detail about the operation that I have not covered, such as the various types of electron microscopes, but I do not wish to bore you with the gorey details of it all. If you want to see more, I would suggest the first source linked below.

I plan on making future posts about the other types of microscopes that can view the nano scale.

Do you think nanotechnology will cause the end of the world because little nano robots self replicate until the whole world and all of its resources are slowly eaten away by them?

Well, believe it or not, this Armageddon scenario has already has been brought up. It is called the “grey goo” scenario as Eric Drexler put it. It is a good thing that, like many doomsday scenarios, it is a gross over statement of the truth. Yes, self replicating bots will replicate at a near exponential rate, but in the end nanotechnology is very specific on the input chemicals. They usually needing the right materials in the right form, not just any compound will work. It also takes a large about of energy to decompose most stable compounds that exist around us.

Even our own body proteins are specific to the chemical inputs. For example, there are two types of glucose (sugar) each has the same atoms each with a nearly identical structure except for one thing. Just like you have a right hand and a left hand you can not make it such that the two hands are the same. No amount of rotation will make the hand look the same, as either the thumb sticks out at opposite sides or one hand you see the palm and the other you see the back of your hand. There exists a right handed version of glucose that we can absorb and a left handed version that we can not absorb. This seemingly minor difference stops us from using the left handed version of glucose. It is the same way with nano bots. In most cases, they are picky eaters. They take in a specific chemical and put out one product. Also in many cases, they are limited to the environment in which they are in, as they require a specific pH level and/or temperature.

This video is over dramatic, but it gives a general idea of the worry surrounding nanotechnology.

If you are a fan of Futurama, there is an episode Benderama where the “grey goo” scenario played out.

I am not saying that nanotechnology is safe and danger free. There is a certain amount of controversy about this end of the world idea. I believe the video over dramatizing the facts. I compare nano bots to bacteria. They act in much the same way. They infinitely self replicate if given the materials, space and conditions to do so, but have they killed our world? No, they have needs that are too specific and cannot break everything down. Even nano bots have one down side compared to bacteria, they will not evolve. In the end, there are dangers associated with any new technology but I believe that we have bigger worries than having the world being eaten up and turned inti a land of “grey goo” at least for now.

As a side note Eric Drexler has been trying to revoke the term grey goo but sadly like all else on the internet, you can’t take things back.